<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>dd</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" type="text/css" media="screen" href="main.css" />
    <script src="简单计算器.js"></script>
</head>
<body>
    <p>简单计算器:</p>
<table border="1" style="position:center;">
  <tr>
    <td>第一个数：</td>
    <td><input type="text" id="first"/></td>
  </tr>
  <tr>
    <td>第二个数：</td>
    <td><input type="text" id="twice"/></td>
  </tr>
  <tr>
    <td colspan="2" >
      &nbsp;
      <button style="width:inherit" onclick="add()">+</button>
      &nbsp;
      <button style="width:inherit" onclick="subtract()">-</button>
      &nbsp;
      <button style="width:inherit" onclick="ride()">*</button>
      &nbsp;
      <button style="width:inherit" onclick="devide()">/</button>
    </td>
  </tr>
  <tr>
    <td colspan="2" rowspan="2">
      <p id="result"></p>
    </td>
  </tr>
</table>
</body>
</html>


